The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 31 |
| 5 | 121 |
| 6 | 605 |
| 7 | 2911 |
| 8 | 13361 |
| 9 | 64255 |
| 10 | 302621 |
| 11 | 1428031 |
| 12 | 6770555 |
| 13 | 31965701 |
| 14 | 151200251 |
| 15 | 715034375 |
| 16 | 3380212751 |
| 17 | 15984722176 |
| 18 | 75579365455 |
| 19 | 357361263031 |
| 20 | 1689760311371 |
| 21 | 7989708622205 |
| 22 | 37778247366211 |
| 23 | 178629122366311 |
| 24 | 844620446404405 |
| 25 | 3993667315453871 |
[1,1,1,5,31,121,605,2911,13361,64255,302621, 1428031,6770555,31965701,151200251,715034375, 3380212751,15984722176,75579365455,357361263031, 1689760311371,7989708622205,37778247366211, 178629122366311,844620446404405,3993667315453871] |